Real Answer: No one knows. It is too far out and too much can change and go wrong. Any number you read is just a guess and will not match the final number. It depends on how affordable, reliable the aircraft is as well as costs, performance and alternatives by then. One big unknown is how effective stealth technology will be on fighters like the F-35. If you would believe American's the F-35 flys on sunshine and is invisible to other fighters, if you believe Russia the stealth on the F-35 does nothing and it is slower, less maneuverable, and less capable than all their jets. Because so much of American stealth technology is classified, it is pretty much impossible to know until an F-35 ends up having a dogfight with the latest non American equivalent. One last factor is the wild card of India's economy, if it stays around 5-6% growth expect one result, it GDP growth booms to 9-11% expect a very different number of 5th generation fighter jets purchased.